
\part{Future Work}
\label{sec:futurework}
While we have discussed many possibilities for future work in
Part~\ref{sec:discussion} we will now mention several areas we believe
would be good next steps. The study of load balancing virtual
operating systems is young but fertile, and interesting systems and
algorithms problems are numerous.

First, work should be done to extend and improve the XenSim
simulator. This will allow work to continue at a more rapid pace than
is possible with real hardware experiments, and will allow rapid
testing of new algorithms. At minimum, extensions to support multiple
processors and more accurate simulation of networking should be
implemented. In addition, the system for determining resource loads
should be rethought and possibly reimplemented. If it is kept in its
current state, work should be done to determine the characteristic
work loads of the real world situations we are trying to simulate.

Studies of real life workloads will also prove useful in developing
the next generation of load balancing algorithms. As discussed in
Section~\ref{sec:performancemodeling}, unlike in process-level load
balancing the task of calculating expected performance is
non-trivial. For this reason, work to predict real-life variations in
page dirtying rates, network usage, and CPU usage will be important to
the future of this subject. 

Utilizing this data, the next generation of balancing algorithms
should be tested in more realistic work load environments. Work
combining short term and long term schedulers under a range of
conditions are likely to produce interesting and useful results.


\part{Conclusion}
\label{sec:conclusion}
Continuing in the tradition of process level load balancing, virtual
operating system load balancing promises to be an interesting and
fruitful field. The challenges of finding configurations which will
perform well in the short and long runs while eliminating unnecessary
and costly migrations are considerable, and we have only begun to
face them. Because of the high levels of flexibility and increased
resource utilization introduced by Xen, we are confident it and other
virtualization solutions like it will continue to gain popularity. As
this happens, strategies for effectively managing large numbers of
virtual machines will become even more important. As a result,
continued work in this field is and important and necessary part of
the future of systems virtualization. 